Apparatus for striping inside seams of cans

ABSTRACT

AN APPARATUS FOR APPLYING AN IMPERVIOUS PROTECTIVE COATING OVER THE SEAMS OF CYLINDRICAL METAL CAN BODIES EITHER BEFORE OR AFTER THE SEAMS ARE WELDED, SOLDERED, OR CEMENTED AND PRIOR TO SPRAY COATING THECOMPLETE INTERIOR OF THE BODIES. THE APPARATUS IS OPERABLE TO INTERMITTENTLY APPLY AN AIRLESS SPRAY TO THE INTERIOR SEAMS OF THE CANS AS THEY CONTINUOUSLY MOVE PAST AN AIRLESS SPRAY GUN SECURED TO THE END OF A STUBHORN OF A CAN FORMING LINE. THE APPARATUS INCLUDES A NEW AND IMPROVED AIRLESS SPRAY NOZZLE WHICH IS OPERABLE TO ATOMIZE THE SPRAY NEARER THE NOZZLE THAN HAS HERETOFORE BEEN POSSIBLE. IT ALSO INCLUDES A PAIR OF AIR JETS LOCATED ON OPPOSITE SIDES OF THE SPRAY AND OPERABLE TO CONFINE THE ATOMIZED SPRAY OR FORG TO THE SEAM OF THE CAN SO THAT LITTLE OR NO EXCESS MATERIAL IS SPRAYED ONTO THAT PORTION OF THE CAN LOCATED ADJACENT THE SEAM.

United States Patent 1191 Rood et al.

111 9 3,815,544 1 June 11, 1974 1 1 APPARATUS FOR STRIPING INSIDE SEAMSOF CANS [75] Inventors: Alvin A Rood, Westlake; Edwin F.

Hogstrom; William C. Stumphauzer, both of Sheffield Lake, all of Ohio[73] Assignee: Nordson Corporation, Amherst, Ohio [22] Filed: Jan. 19,1971 [21] Appl. N0.: 107,632

[52] US. Cl 118/2, 118/317 [51] Int. Cl. B05c 11/00 [58] Field of Search118/2, 317; 239/291, 412,

15.6] I 'i References Cited 1 UNlTED STATES PATENTS 2,693,782 11/19542,895,449 7/1959 2,961,990 11/1960 3,081,947 3/1963 3,208,673 9/19655/1966 3,405,679 10/1968 Nor'risctalml ..ll8/2 3,526,027 9/1970Manueletah. 118/317 Primary Examiner-Mervin Stein AssistantExaminer-.Leo Millstein Attorney, Agent, or Firm-Wood, Herron & Evans 57ABSTRACT An apparatus for applying an impervious protective coating overthe seams of cylindrical metal can bodies either before or after theseams are Welded, soldered, or cemented and prior to spray coating thecomplete interior of the bodies. The apparatus is operable tointermittently apply an airless spray to the interior seams of thecans'as they continuously move past an airless spray gun secured to theend of a stubborn of a can forming line. The apparatus includes a newand improved airless spray nozzle-which is operable to atomize the spraynearer the nozzle than has heretofore been possible. It also includes apair of air jets located on opposite sides of the spray and operable toconfine the atomized spray or fog to the seam of the can so that littleor no excess material is sprayed onto that portion of the can locatedadjacent the seam.

13 Claims, 7 Drawing Figures PATENTEDJUH 1 1 mm 3 13 15544 SHEET 3 or 3xxx! APPARATUS FOR STRIPING INSIDE SEAMS OF CANS This inventionrelatesto the application of protective coatings to the interior ofmetal cans and more particularly to the application of a stripe ofprotective coatings to the interior soldered, welded, or adhered seam ofa three-piece metal can.

Metal cans are made by either one of two processes. One process, thetwo-piece can process, involves form ing a drawn cup from acylindricalslug of metal and then deep drawing the cup to a can configuration. Theother process, the three-piece process, involves forming a cylindricalcan body from a sheet of metal and then attaching two lids or ends totheopposite ends of the body. The invention of this application isconcerned only with the application of protective coatings tothree-piece cans.

In the manufacture of three-piece cans, the cylindrical bodies areformed by wrapping a sheetof metal around a so-called stubhorn. Prior toformation into, the cylindrical configuration, the sheets 13 aregenerally roller coated on all but the lateral edges with a protectivecoating of lacquer or other similar material. After formation into thecylindrical, configuration, the lateral edges of the sheet are eitherbutted or overlapped and secured togetherby either a welded seam, asoldered seam, or a cemented seam. The seam area and the previouslyuncoated lateral edges of the. sheet are thenspray coated with an epoxyor phenolic lacquer or some modification of these materials.Subsequently, the complete interior of the cylindrical body is coatedwith another complete protective coating which is generally of vinyllacquer although numerous other materials, as, for. example, resins,lacquers, waxes and paints, are applied for this same purpose, i.e., toafford protection of the contents of the can against contamination bythe metal. Particularly, beer, beverages and foods must be protected inthis way against metal contamination by the application of a tastelessand odorless protective coating material to the interior of the can.

The protective material which is applied to the interior of the can mustbe continuous throughout the entire interior surface. Any pin holes,cracks, or imperfections in the integrity of the coating render thecanunsuitable for most applications. To avoid pin holes, cracks, orimperfections in the coating, it is now common practice in the canindustry to first apply a stripe of protective material over theinterior seam of a threepiece can body before asecond orsubsequent-layeris applied to the complete interior of the can. The purpose of thisstripe is to provide an impervious layer of protective material overthat portion of the body which is most vulnerable to'imperfections andwhere failures most often occur.

ln co-pending application Ser. No. 56,304filed July 20, l970, andassigned to the assignee of this application, there is described anairless spray technique for applying a stripe of protective material orlacquer to the interior seams of cans as the cans pass over and off theend of the stubhom of a can manufacturing line. This invention is animprovement upon the method and apparatus described in that-application.

Specifically, there is described in that application an airless spraytechnique for intermittently applying a stripe of lacquer to the insideseams of can bodies as the cans pass an airless spray nozzle attached tothe end of the stubhorn. The spray nozzle is so positioned on thestubhom that it is located on the interior of the can bodies as thebodies pass the striping station.

One of the problems encountered in spraying a stripe of protectivematerial onto the seam of a can body is that of confining the spray to astripe approximately to 1 inch in width, depending upon the canapplication, without having the spray bounce up or fog onto the area orside of the can wall adjacent the stripe. This confining of the stripeto avoid .its overlapping or splashing onto the side walls of can bodiesis particularly critical in the case of soldered seam cans. Commonpractice is to spray the seam of the can with the protective stripeprior to soldering of the seam but after the seam has been formed andoverlapped. After spraying, the seam is soldered and the area adjacentthe seam is exposed during soldering to a temperature of 700-900 Fduring which the stripe of protective material is cured. Thereafter, thecomplete interior of the can body is sprayed with a coating of lacqueror protective material but one which cures at a lower temperature, as,for example, 300 F. If any high curing temperature seam stripingmaterial inadvertently is sprayed onto the area adjacent the stripe,that lacquer is not subjected to the 700900 F. seam temperature and istherefore never cured, either during the soldering operation orduring'the'subsequent curing of the low curing temperature materialsprayed onto the complete interior of the can. i

It hastherefore been a primary objective of this invention to provide anew and improved apparatus'for applying a continuous stripe ofprotective material or lacquer over the interior seam of a can withoutsplashing, spraying, or bouncing protective material off the seam areaonto the sides of the can body-adjacent the seam area.

Still another objective of this invention has been to provide anapparatus for'spraying a stripe of protective material over the seam ofa can with a minimum quantity of material while still obtaining acontinuous uniform coating of material over the seam.

These objectives are accomplished and one aspect of this invention ispredicated upon the utilization of a new and improved nozzle forspraying the stripe of liquid protective material onto the seam of acan. This nozzle. has an axial bore terminating in afan-shapedheretofore been the most troublesome aspect of inside stripingof cans, the bounce or splash of the spray onto and up the side walls ofthe can.- This splash, or socalled overspray area, is never completelycured and as a consequence causes defective cans.

Still another aspect of this invention is predicated upon the concept ofutilizing two air nozzles located alongside the liquid spray nozzle tocontain the edges of the atomized spray to the can seam area. In thepreferred embodiment, these air nozzles are so connected to the gun thatthe air spray is turned on and off simultaneously with the intermittentemission of liquid spray 3 from the protective material nozzle. The aircurtains which emerge from these air nozzles are generally fanshaped andcontain the liquid spray fog along the edges so as to prevent that fogfrom rolling out onto the area adjacent the stripe. V I

Still another'aspect of this invention is predicated upon the empiricaldetermination of nozzle design and conditions under which an airlessspray stripe may be applied to the interior seam of a can body in auniform continuous film which meets all can industry standards in termsof continuity, uniformity, weight of material, and application of thestripe to a confined area.

Still another aspect of this invention is predicated upon thedevelopment of a new and improved nozzle which has better sprayatomization characteristics .,close to the nozzle orifice than hasheretofore been possible.

These and other objects and advantages of this invention will be morereadily apparent from the following description of the drawings inwhich:

FIG. 1 is'a diagrammatic illustration of a portion of a can forming lineincluding the invention of this application. 2

FIG. 2 is an enlarged view,1partially in cross section, of the end ofthe can forming line stubhom of FIG. 1.

FIG. 3 is an end elevational view of the end of the stubhom includingthe spray gun taken on line 3-3 of FIG. 2. V

FIG. 4 is a cross sectional view through the spray gun of FIG. 1. l

FIG. 5 is another cross sectional view through the spray gun taken in aplane normal to the plane of FIG.

FIG. 6 is an enlarged cross sectional view through the spray nozzletaken on line 6-6 of FIG. 2.

FIG. 7 is a top plan view of the spray pattern which emerges from theliquid spray nozzle and the two air nozzles of F I6.-6.

Referring first to FIG. 1, there is illustrated diagrammaticallyastandard can production line used in the production of cylindrical canbodies. This line includes a stubhom 10 which serves as a mandrelaroundwhich can bodies 11 are formed as they pass downstream. The can bodies11 are moved longitudinally over the stubhorn from a magazine 12 by lugson a chain conveyer which engage the rear edge 13 of the bodies and pushthem along the stubhorn. As bodies'pass off the stubhorn, after havingbeen formed into cylindrical configuration, they move into a network ofrails 15 through which they then pass during continued formation of thecans.

In the final stages of movement of thecan bodies over the stubhom 10,the ends of the sheet metal from dies pass off the stubhom 10 and intothe rails 15', they are passed through an inside striping stationindicated by the numeral 16. At this station a stripe of protectivematerial 17 (FIG. 7) is sprayed over the overlapped.

seam l8.of the can. Soldered can bodies then require passage through asoldering station downstream of the striping station 16 to completeformation of the seam but the adhered and welded seams are completelyformed when the bodies enter the rails 15.

In order to apply the stripe 17 of protective material over the seamarea A (FIG. 7) of the can body, a spray gun 20 is secured to the end ofthe stubhom 10. This gun is so positioned that the can bodies pass overit before passing into the rails 15.

The gun 20 is secured to the end surface 21 of the stubhom by agenerally U-shaped bracket 22 secured onto the end of the stubhom by aplurality of bolts 23. Bolts 19 similarly secure the gun 20 to theopposite or downstream end 24 of the bracket 22. The bracket 22 may beomitted and, in fact, in one preferred embodiment is omitted in whichcase the gun 20 is secured directly onto the end of the stubhorn.

The spray gun 20 is of the so-called circulating flow type; that is,there is a continuous flow of liquid or coating material to the gunthrough a liquid inlet line 25. There is also continuous flow of liquidor coating material from the gun via a line 26 (FIGS. 4 and 5). Asaresult of this continuous flow, the temperature of the liquid materialmay be maintained constant in the gun even when the gun is not in useand when the liquid would otherwise be stationary in the gun, Some canprotective materials set up or harden at room temperature so that it isimportant that these materials not .be

a permitted to stand and become hardened in the gun.

The circulating flow of liquid through the gun precludes this hardeningor setting of the material. In the case of other protective materialswhich are applied at ambient or room temperature, temperaturecontrol isnot as important and a conventional non-circulating or one-fluid linegun may be used. I

The gun contains a check valve, indicated generally by the numeral 30,operable, to open and close a passage 31 leading to an orifice 32 of anozzle 33 in synchronization with movement of cans past the orifice 32.The check valve is pneumatically opened by air pressure supplied to thegun via an air line 35 and is spring biased to a closed position. Airpressure at approximately psi is supplied to the gun in the line 35 froman air pressure source 36 through a solenoid controlled valve 37. Anelectric photocell circuit including a photocell 38 and receiver 39control the flow of electric current to the solenoid of the valve 37.The sender is operable to direct a light beam through a hole 41 in thestubhom 10 so that cans entering the striping station 16 break thecircuit and trip a solenoid 42, thereby causing the valve 37 to beopened and air pressure supplied via line 35 to the gun.

The solenoid valve portion of the valve 37 is an onoff solenoid valve.It is used in combination with a conventional four-way spool valve 42,to one end of which air is alternately supplied from a source 36 at apressure of approximately 60 psi or to which air is vented to atmosphereunder the control of the solenoid. Air of lesser pressure (as, forexample, 20 psi) is supplied through the line 43 to the opposite end ofthe spool within valve 37 at all times, so that when the solenoidelectrical circuit is broken, the solenoid valve connects the highpressure end of the spool valve 37 to atmospheric pressure and a lowpressure (20 psi) at'the opposite end then moves the spool toward thehigh pressure end. When the electrical circuit again energizes thesolenoid, the valve 37 connects the high pressure end of the spool to 60psi, and the spool immediately moves toward the low pressure end againstthe resistance offered by the low air pressure in line 43. It has beenfound that the valve 37 may be more reliable with a low pressure lineconnected to the one end of the valve than it is when it utilizes springreturn. It has also been found that the solenoid valve may act fastenough when used as a pilot valve to control flow to the gun but that ifused with higher flow capacities without a second stage spool valve itmay be too slow to keep up with current can production lines.

Referring again to FIGS. 4 and 5, it will be seen that the gun generallycomprisea a two-piece cylindrical body 45 within which there is an axialor central bore 46. This bore comprises a fluid chamber 47 adjacent thefront end of the body, a smaller diameter connecting chamber 48, and alarge diameter piston chamber 49. The rear side of the piston chamber 49is open to the atmosphere through a small diameter section 51 of thebore 46. An end cap 52 is secured to the body 45 by bolts (not shown)and closes the fluid chamber 47. The cap 52 comprises a central disc 53from which hub sections 54, 55 extend rearwardly and forwardly,respectively. The rearward hub 54 fits within, and with an O-ring, sealsthe fluid chamber 47. The forwardly extending hub section 55 has aninwardly extending flange 56. An axial bore 57 extends through the cap52 and comprises a large diameter rear section 58 and a smaller diameterfront section 59.

A cylindrical metal insert 61 made from a hard material, as, forexample, tungsten carbide, is brazed or otherwise fixedly secured withinthe small diameter section 59 of the cap. This insert 61 defines theseat of the i check valve 30. The insert has a stepped axial bore whichcomprises a large diameter rearward section 62,

and the small diameter passage 31 interconnected by shoulder 63. Anarcuate seat is machined into the shoulder at the point where theshoulder joins thesmall bore 31. This seat is configurated to cooperatewith a generally semispherical end 64 of the check valve head 65 to forma seal.

The nozzle assembly 33 is bolted onto the flanged end 56 of the end cap52. Referring to FIGS. 4 and 6, it will be seen that this assembly 33comprises a nozzle mounting block 70 and a carbide nozzle tip 71. Theblock 70 is fixedly secured onto the end cap by 'a pair of bolts 72.This block 70 has one bore 73 which communicates with and is coaxialwith the outlet passage 31 of the gun and a second passage 74 whichintersects at 90 the first passage 73. This second passage 74 alsointersects the apex of an inverted V-shaped groove69, formed in thebottom of the block 70. This second bore or passage 74 extendscompletely through the block 70 and has a small diameter threaded endsection 75, an intermediate diameter section 76, and a counterbored endsection 77. The carbide tip 71 is brazed or otherwise fixedly secured inthe intermediate section 75 with a shoulder 78 of the tip abutting thecounterbored shoulder of the bore 74.

The tip 71 has an axial central bore 79 extending through it andintersected at a right angle by a transverse bore 81. The bore oraperture 81 communicates with and is coaxial with the bore 73 of themounting block 70 so that liquid may be transmitted through the bore 73into the nozzle bore 79.

There is a nozzle clean-out screw 82 threaded into the threadedsmalldiameter section 75 of the bore 74. The end 83 of this screw is spacedfrom the rear end surface 84 of the nozzle tip so that a turbulencechamber 85 is defined by the rear surface 84 of tip 71, intermediatesection of the bore 74, and the inner end 83 of the screw 82. Asexplained more fully hereinafter, it has been found that the presence ofthis turbulence chamber in combination with the injection of liquid intothe axial passage 79 of the nozzle tip through the transverse bore 81markedly improves the atomization characteristics of the nozzle.

The outer end of the nozzle tip 71 is generally hemispherical inconfiguration. The elliptical-shaped orifice 32 is machined into the topof the dome so as to intersect at a right angle the axial orifice 79 ofthe tip. Conventionally, this elliptical orifice is machined into thedome by a tapered grinding wheel. Liquid emerging at a high pressure oras a high pressure stream (as, for example, at 200 to 1,000 psi) fromthe elliptical-shaped orifice atomizes and assumes the ellipticalpattern depicted by the dashed line 87 of FIG. 7.

Referring back to FIG. 6, it will be seen that as the high pressurestream of liquid emerges from the nozzle orifice 32 it spreads out orfans out to form a generally fan-shaped solid curtain 88 of liquid. Asthe curtain moves away from the nozzle, ripples or waves form in it, asindicated by the numeral 89. The ripples then break up into longitudinalligaments, indicated by the numeral 91. These ligaments subsequentlybreak up as they move away from'the nozzle into droplets which thenatomize into a fine meral 92.

In order to'apply a sufficiently thin film of lacquer or other coatingmaterial to the seamarea A of a can and to limit the sprayed material tothe stripe area or to the area immediately adjacent this stripe area,the film must be finely atomized before it strikes the can surface. Ifnot sufficiently atomized, the spray or fog strikes the substrate, orthe can side wall, with sufficient velocity and impact that it bouncesand splashes onto the can side wall to form an oversprayed area on thearea adjacent the seam area A.

One aspect of this invention is predicated upon the determination thatthe overspray problem or the splash problem is materially reduced oreliminated by the turbulence chamber 85. Byinserting a threaded plug orscrew 82 into the threaded bore 75 of the nozzle mounting block buthaving the end 83 of the screw terminate short of the rear surface 84 ofthe nozzle tip 71, there is provided a turbulence chamber 85 immediatelybehind the nozzle tip. This turbulence chamber in combination with theinjection of liquid into the nozzle tip via a radial port 81 has theeffect of materially reducing the distance D required for the spray toatomize after emerging from the nozzle orifice 32. Specifically, it hasbeen found that this arrangement reduces the distance D to approximatelyone-fifth the distance otherwise required for atomization when the sameliquid is directed axially through the same size nozzle tip at the samepressure and temperature. When thedistance D is reduced, the degree ofatomization of the spray is improved and the velocity with which itstrikes the substrate or can body is materially reduced. This fineratomization and reduction of particle velocity in turn spray, asindicated by the nu- -eliminates the problem of the spray bouncing andclimbing up the side walls 93 of the can outside the can stripe area A.

To further contain the finely atomized fog which results from thisimproved nozzle, a pair of air curtains v 7 p 94, 95 are preferablyprovided adjacent the opposite ends of the elliptical-shaped pattern 87of the liquid spray. These curtains are also elliptical in crosssectional configuration at the point where they strike the substrate orcan body adjacent the stripe 17. As indicated by the cross hatchedpatterns 94A, 95A in FIG. 7, these air curtains 94, 95 have the effectof chopping off the ends 87A, 87B of the fan-shaped pattern 87 ofatomized liquid spray so as to confine it to a width W.

To create the air curtains 94, 95, air is supplied to a pair ofelliptical-shaped noule orifices 97 and 98 in a pair of nozzles 99 and100. This air is supplied to the nozzles in synchronization with openingand closing of the check valve 30 of the gun 20. To this end, thenozzles 99 and 100 are mounted in the ends of tubes 101 which extendupwardly and are mounted-in a. manifold block 102 secured to the gun.The block 102 has a central passage 103 which communicates with thepassages within the tubes 101. The passage 103 is supplied with airunder regulated pressure of from to 70 psig from the pneumatic line 35.It is also connected to a pneumatic line 35A ofv the gun. Consequently,air is supplied to the nozzles 99 and 100 in synchronization withopening and closing of the check valve of the gun.

In operation, can bodies 11 are formed over the stubhorn l0 atthe rateof approximately 550 plus or minus 50 cans per minute. This rate variesfrom one can man ufacturer to another, but quite commonly today averagesapproximately 575 can bodies per minute per line in the production ofstandard beer or beverage cans. As

i the cans move along the stubborn, a solder, adhesive or weldiscommonly applied to the overlapping or abutting edges 18 of the sheet attheseaming station 14. This station is located immediately in front ofthe striping station 16 where the stripe 17 of protective material fromthe nozzle 33 and spray gun 20 is directed onto the seam. In the case ofsoldered cans, the seam is subsequently completed and the stripingmaterial simultaneously cured by the application of soldering heatto theseam at a subsequent soldering station. Generally, this heat raises thetemperature of the seam to above 7009-900 F. so as to cure theprotective coating of the stripe during the'soldering operation. In thecase of seam welded or seam adhered cans, the striping mate rial iseither heat or air cured at a much lower temperature farther down thecan production line.

The emission of liquid spray from the nozzle 33 and the emission of theair curtains from the nozzles 99 and 100 are turned. on and off insynchronization with movement of the can bodies 11 over the stubhorn andthrough the striping station. This is accomplished by the can bodiesinterrupting alight beam of the photocell sender and receiver unit 38,39. Upon interruption of the light beam and after a predetermined timedelay built into a solenoid control circuit, the solenoid controlcircuit is operable to shift the solenoid and move a valve spool of thevalve 37 so as to connect the air line to the source of air pressure 36,thereby connecting a forward end chamber 104 of the check valve controlpiston chamber to high pressure, i.e., 60 psi air. This results inmovement of a piston 105 and opening of the check valve 30. Upon openingof this valve, the liquid protective material in the fluid chamber 47 isallowed to pass from the liquid chamber 47 past the head of the valveinto the conduit or passage 31 and subsequently to the nozzle orifice 32of the nozzle 33. Liquid in the chamber 47 is maintained at a pressureof approximately 250-800 psi, the pressure at which it is supplied by apump 106 from a reservoir 107. I

A predetermined time after interruption of the light beam, that canwhich has broken the light beam passes out of alignment with the nozzle33. After that predetermined time, a timer circuit interrupts the signalto the solenoid causing it to be tie-energized and the control circuitto be reset preparatory to interruption of the light beam by the nextfollowing can. Upon deenergization of the solenoid, low air pressure,i.e., 20 psi, in line 43 or spring pressure then moves the spool of thevalve 37 to the position in-which the air line 35 is connected toatmospheric pressure. This results in the venting of line 35A of thegun, causing the check valve 30 to be closed, which immediately cuts offthe flow of liquid spray from the nozzle orifice 32 and the emission ofair from the nozzles 99 and 100 until the next following can againinterrupts the light beam.

In one preferred embodiment, the protective material applied to the canseam of a soldered seam beer can 2 1 1/ l 6 inches and 4 1 1/16 inchesin length is an epoxy resin coating material manufactured by the DeSotoChemical Company of Chicago, Illinois, and designated as their No.563-803 Epoxy Resin Can Coating. It is supplied to the nozzle at atemperature of I-190 F. at a pressure of approximately 400 psi and at aZahn No. 2 cup viscosity of 16 seconds, 77 F. The preferred nozzle isone which has a flow rate of 0.015 gallons per minute of water at 500psi and at ambient temperature. The nozzle orifice is preferably spaced1 A inch from the can seam and lays down a protective strip of material9/16 inch to 1 1/16 inch in width W. The resulting stripe of materialwhen subsequently cured weighs ap-.

proximately 5 or 6 milligrams. Including theoverspray, this stripe neverexceeds 1 1/16 inch in width W, which width is adequately heated tocuring temperature of approximately 750 F. during the subsequentsoldering operation.

Prior to this invention it has been difficult to control the applicationof spray to a can seam so as to avoid overspray and material beingapplied to the side walls of the can over so wide an area that thematerial remained uncured even after the subsequent soldering operation.Primarily, the problem occurred because of the atomized spray bouncingoff the seam stripe area of the can and rolling up the inside walls ofthe can into areas adjacent the stripe area, which areas never subseWhile we have described only a single preferred embodiment of ourinvention, persons skilled in the art to which this invention pertainswill readily appreciate numerous'changes and modifications which may bemade without departing from the spirit of our invention. For example,those persons skilledin the can manufacturing art will readilyappreciate that the striping apparatus of this invention is equallyapplicable to outside can striping as to inside can striping. Therefore,we do not intend to be limited except by the scope of the appendedclaims.

Having described our invention, we claim: 1. Apparatus for applying animpervious protective coating to the longitudinal seams of spacedcylindrical can bodies as the can bodies move through a striping stationof a can body forming line over which can bodies are formedintocylinders, which apparatus comprises an airless liquid spray noule,means for securing the nozzle on a can assembly line in a position inwhich the nozzle has its orifice directed toward the seam of a formedbody,

means for forcing an airless spray fan of liquid coating material athigh pressure from the nozzle orifice and directing it in a stripe ontothe surface of the seams of the can bodies, and

means for starting and stopping the emission of airless spray from thenozzle orifice in synchronization with movement of the spaced can bodiespast the nozzle so that the airless spray is directed onto a seam of acan body as the body passes the nozzle orifice but it is turned offafter that can body passes the nozzle orifice until the seam of the nextfollowing can body moves into alignment with the orifice, theimprovement wherein said airless spray nozzle has a first axial passage,said passage terminating at one end in a spray orifice,

said nozzle having a second liquid injection passage intersecting saidfirst passage at approximately a right angle at a point spaced from saidorifice, and

' fice directed toward the interior seams of the formed cans.

3. The apparatus of claim l'in which the airless spray nozzle orificehas a flow rate of less than 0.040 but more than 0.005 gallons perminute of water at 500 pounds per square inch pressure.

4. The apparatus of claim 1 in which the liquid forcing means isoperable to force the coating material from the nozzle orifice at apressure less than 800 pounds per square inch but more than 200 poundsper square inch.

5. The apparatus of claim 1 in which the airless spray nozzle orificehas a flow rate of about 0.015 gallons of water per minute at 500 poundsper square inch pressure.

6. The apparatus of claim 1 in which the means for forcing the coatingmaterial from the nozzle is operable to force the material from thenozzle orifice at a pressure of about 400 pounds per square inch.

7. The apparatus of claim 1 which further includes a pair of airnozzles-located on opposite sides of said liquid spray nozzle and meansfor supplying air under pressure to said pair of air nozzles and fordirecting an air curtain emerging from said nozzles onto the interiorsurface of the can bodies on opposite sides of the seam so as to containand limit the liquid spray to the seam area of the can bodies.

8. The apparatus of claim 7 which further includes means for startingand stopping the emission of theair curtains from the air nozzles insynchronization with the starting and stopping of the emission of liquidspray from the liquid spray nozzle.

9. Apparatus for applying an impervious protective coating to thelongitudinal seams of spaced cylindrical can bodies as the can bodiesmove through a striping station of a can body forming line over whichcan bodies are formed into cylinders,'which apparatus comprises anairless liquid spray nozzle, means for securing the nozzle on a canassembly line in a' position in which the nozzle is located interiorlyof the cans and has its orifice directed toward the interior of theseams of formed can bodies,

means for forcing an airless spray fan of liquid coating material athigh pressure from the nozzle orifice and directing it onto the interiorsurface of the seams of the can bodies, and Y y means for starting-andstopping the emission of airless spray from the nozzle orifice insynchronization with movement of the spaced can bodies past the nozzleso that the airless spray is directed onto a seam of a can body as thebody passes the-nozzle orifice but is turned off after that can bodypasses the nozzle orifice until the seam of the next following can bodymoves into alignment with the orifice, the improvement wherein saidairless spray nozzle has a first axial passage, said passage terminatingat one end in a generally elliptical-shaped orifice,

said nozzle having a second liquid injection passage intersecting atapproximately a right angle said first passage at a point spaced fromsaid orifice, and

a turbulence chamber of greater cross sectional area than said firstpassage intersecting and coaxial with said first passage, theintersection of said turbulence chamber and said first passage beingspaced from the intersection of said first and second passages in adirection away from said orifice.

10. The apparatus of claim 9 which further includes a pair of airnozzles located on opposite sides of said liquid spray nozzle and meansfor supplying air under pressure to said pair of air nozzles and fordirecting an air curtain emerging from said nozzles onto the interiorsurface of the can bodies on opposite sides of the seam so as to containand limit the liquid spray to the seam area of the can bodies.

11. The apparatus of claim 10 which further includes means for startingand stopping the emission of the air curtains from the air nozzles insynchronization with the starting and stopping of the emission of liquidspray from the liquid spray nozzle.

12. Apparatus for applying an impervious protective coating to thelongitudinal seams of spaced cylindrical can bodies as the can bodiesmove through a striping station of a can body forming line over whichcan bodies are formed into cylinders, which apparatus comprises anairless liquid spray nozzle, means for securing the nozzle on a canassembly line in a position in which the nozzle is located interiorly ofthe cans and has its orifice directed toward the interior of a seam of aformed body,

means for forcing an airless spray fan of liquid coating material athigh pressure from the nozzle orifice and directing it onto the interiorsurface of the seams of the can bodies, and

means for starting and stopping the emission of airless spray from thenozzle orifice in synchronization with movement of the spaced can bodiespast the nozzle so that the airless spray is directed onto a seam of acan body as the body passes the nozzle orifice but is turned off afterthat can body passes the nozzle orifice until the seam of the nextfollowing can body moves into alignment with the orifice, theimprovement wherein,

said airless spray nozzle has a first axial passage extendingtherethrough, said passage being threaded at one end and adapted toreceive a nozzle tip at the opposite end,

a screw threaded into said threaded end of said passage,

a nozzle tip mounted in said opposite end of said passage, said tiphaving an axial passage extended therethrough and coaxial with saidaxial passage of said mounting block, said tip axial passage terminatingat its outer end in a generally ellipticalshaped orifice,

said tip having a second liquid injection passage intersecting atapproximately a right angle said tip axial passage at a point spacedfrom said orifice, and

a turbulence chamber located in said mounting block axial passagebetween the inner end of said screw and the inner end of said tip, saidchamber being of greater cross sectional area than said axial passage ofsaid tip.

13. The apparatus of claim 12 in which said turbulence chamber isdefined in part by the inner end of said screw and in part by the innerend of said tip.

